Heartbreaking stories of seabirds eating plastic — and the accompanying horrible images— are everywhere, but now scientists are an important question: Why do seabirds eat plastic in the first place? And why are some more likely to have bellies full of plastic than others?The answer, it turns out, lies in a compound called dimethyl sulfide, or DMS, which emits a “chemical scream” that some birds associate with food. When seabirds find chunks of plastic bobbing in the water, they gobble them up, not realizing that they’ve just consumed something very dangerous.